Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 13, 1950 UNHE STES at; F H C ANTIOXIDANTS FOR ltflNERAL OIL LUBRI- CANTS AND COMPOSITIONS CONTAINING THE SAME vania No Drawing. Application December 8, 1948, Serial N- 64,237

15 Claims.

This invention relates to antioxidants for mineral oil lubricants and compositions containing the same,. and more particularly, it relates to addition agents for mineral oil lubricants which inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.-

The formation of varnishes, gums and sludge on engine surfaces is due at least in part to oxidation effects on mineral lubricating oils. In turbine oils the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubricants which will inhibit the oxidative deterioration of such lubricants.

It is a further object of this invention to provide improved mineral oil lubricant compositions which are remarkably stable against oxidation under service conditions.

These and other objects are accomplished by the present invention wherein an addition agent for mineral oil lubricants is prepared by condensing diphenylamine, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst, and recovering the condensation product. The condensation product so obtained is a lightcolored product which, when added to mineral oil lubricants, confers a remarkable stability against deterioration by oxidation. Such condensation products and the mineral oil lubricant compositions containing them are believed to be novel and are considered parts of our invention. Contrary to what may be expected from the nature of the reactants, we do not obtain highly condensed, insoluble resinous products. On the contrary, when the above reactants are condensed in accordance with our invention, there are obtained light-colored condensation products which are non-resinous and which are readily soluble in mineral oils.

In performing the condensation, the reactants are mixed and heated to a maximum temperature of 350 F. We have found that if the temperature of 350 F. is exceeded to any substantial extent, the condensation product formed tends to be resinous andinsoluble. In general, the pre- 2 ferred temperature for the condensation ranges from to 300 F.

The proportions of the reactants vary over a fairly wide range. The diphenylamine is employed in an amount of from 1 to 4 mols; N-dimethylaniline is employed in' an amount of from 1 to 7 mols; and the amount of formaldehyde used is from 1 to 7 mols. Ordinarily, it is preferred to use from 5 to 10 per cent by weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as 1 per cent by weight, and larger amounts, as high as 20 per cent by weight, may also be employed; but larger amounts than about 10 per cent by weight are ordinarily not necessary.

In, lieu of formaldehyde, any formaldehydeyielding compound, such as paraformaldehyde, dioxymethyleneand trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term formaldehyde is intended to. include formaldehyde-yie1ding compounds as Well as formaldehyde itself.

Various activated clay catalysts may be employed in accordance with our invention. Such materials are well known in the art and comprise a natural clay, such as bentonite, fullers earth floridin and smectite, which has been acid treated in order to activate the clay. These materials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the reactants and catalyst are placed into a reaction vessel which is then closed and the mixture heated with agitation under reflux until all of the formaldehyde or formaldehyde-yielding compound has been consumed. At this time, the water which is formed as a result of the condensation is removed, preferably under vacuum, and the dehydrated condensation product is then filtered to remove the activated clay catalyst. In some instances, it is desirable to prepare our new addition agent in a concentrate in a mineral lubricating oil which may then be diluted down with additional oil to the concentration desired in the final lubricating composition. In such instances, the mineral lubricating oil may be added in a suitable amount, say in a weight equal to the weight of reactants, to the reaction mixture in the reaction vessel, and the condensation product obtained will then be a concentrated solution of the addition agent in the mineral lubricating oil.

The condensation products obtained in accordance with our invention are liquids or crys-r talline solids. While the exact nature of the chemical composition of the condensation products is unknown, all of the three reactants enter into a flnal unitary product. The exact manner in which the catalyst influences the reaction is unknown. However, regardless or any theory involved, the use of an activated clay catalyst is an essential feature of our invention, since if the catalyst is omitted, black, insoluble. resinous condensation products are obtained.

The following examples illustrate the preparation of our new addition agent:

Example L-Into an iron vessel, there was introduced 1 mol of diphenylamine (170 parts by weight), 1 mol of N-dimethylaniline (121 parts by weight) and 1 mol of formaldehyde in a 37 per cent by weight aqueous solution (85 parts by weight). To this mixture, there was added 29 parts by weight of Filtrol (an activated montmorillonite catalyst). The vessel was closed and attached to a reflux condenser. The mixture was then heated to 210 F. and refluxed for 8 hours. then dried by distilling off all water, both that added with the formaldehyde and formed in the reaction, by heating to 280 F. under reduced pressure. The product was then flltered. It had the following properties:

Gravity, API 4.7 Color, NPA 2.0 Neutralization No. 0.4

Gravity, API 6.2 Color, NPA 2.0 Neutralization No. 0.6

Example IIL-Another antioxidant was pre- The condensation product was pared under the conditions outlined in Example 5 I using 2 mols of diphenylamine, 5 mols of N-dimethylaniline, 7 mols ff formaldehyde and 10 per cent by weight of Filtrol (activated montmoriilonite). The filtered product had the following properties:

Gravity, API 5.7 Color, NPA 1.75 Neutralization No. a 0.5

Example III.Another antioxidant was prepared under the conditions outlined in Example I using 2 mols of diphenylamine, 5 mols of N-dimethylaniline, 7 mols of formaldehyde and 10 per cent by weight oi' Filtrol (activated montmorillonite). The flltered product had the following properties:

Gravity, 'API 5.! Color. NPA 1.75 Neutralization No. 0.5

sired in the flnal mineral oil lubricant composition. As stated, our new addition agents are remarkably effective in inhibiting the oxidative deterioration of mineral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally sumcient, For example, our addition agents may be added to mineral lubricating oils in minor amounts, say from 0.001 to 1 per cent by weight on the mineral oil, suflicient to inhibit the oxidative deterioration of the 01]. larger amounts of our new addition agents may be used if desired but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant effects of our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subiected to a standard oxidation test which measures the stability of the oils to oxidation. The oxidation test referred to is a standard test designated ASTM D9434! T. Briefly, the test comprises subjecting the oil sample to'oxygen at a temperature of 0. (203 F.) in the presence of water and an ironcopper catalyst, and determining the time required to build up a neutralization number of 2. The flow of oxygen is maintained at 3 liters per hour. The remarkably effective stability to oxidation of mineral oillubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example IV.--An improved steam turbine oil was prepared by treating a turbine oil base stock with 0.5 per cent by weight of an additive prepared according to Example I. 'A comparison of the properties of the base oil and improved turbine oil showed the following:

Example V.An improved motor lubricating oil was prepared by treating a motor lubricating base stock SAE 30 with 0.5 per cent by weight of,

the antioxidant prepared according to Example II. A comparison of the properties of the base oil and the improved oil showed:

Base improved on on Gravity, API s1.2 31.4 Viscosity, SUV: 1!... 241 no 00101, NPA as as Oxidation Test, ASTM DM3-47T an r., s

L Oxygen per Hm Time Oxidized, H 210 3,200 Neutralization No- 2. 0 2. 0

dimethylaniline.

be either pro-oxidant or to show no antioxidant eifects whatsoever. For example, we have prepared condensation products similar to our new addition agents by substituting xylidine for the The resulting condensation products were found to be entirely unsuitable for inhibiting the oxidative deterioration of mineral oil lubricant compositions.

While we have shown in the examples the preparation of compounded lubricating oils, our invention is not limited thereto but comprises all mineral oil lubricant compositions containing our new addition agents, such as greases and the like. If desired, other known addition agents may be incorporated into the lubricant compositions prepared in accordance with our invention. For example, pour point depressants, extreme-pressure agents, viscosity index improvers and the like may be added.

Resort may be had to such modifications and variations as fall within the spirit of the invention and thescope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 4 mols of diphenylamine, 1 to '7 mols of N-dimethylaniline, and 1 to '7 mols of formaldehyde in the presence of an activated clay catalyst at a temperature not in excess of 350 F. to condense together the three reactants, and recovering the condensation product.

2. The process ofv preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 4 mols of diphenylamine, 1 to '1 mols oi N-dimethylaniline, and 1 to '7 mols of formaldehyde in the presence of an activated.

clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

3. The process of preparing an addition agent for mineral oil lubricants which comprises adding from 1 to 4 mols'of diphenylamine, 1 to '7 mols of N-dimethylaniline, 1 to 7 mols of formaldehyde and from 5 to per cent by weight on the foregoing reactants of an activated clay catalyst to a mineral lubricating oil, heating themixture at a temperature of from 150 to 300 F.

' to condense to ether the three reactants, and recovering a solution of the condensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of diphenylamine, 1 mol of N-dimethylaniline and 1 mol of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

5. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of diphenylamine, 7 mols of N-dimethylaniline and 7 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

6. The process of preparing an addition agent for mineral oil lubricants which comprises heating 2 mols of diphenylamine, 5 mols oi N-dimethylaniline and '7 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 1'. to condense together the three reactants, and recovering the condensation product.

I. A non-resinous condensation product of 6 from 1 to 4 mols of diphenylamine, 1 to '1 mols of N-dimethylaniline and 1 to 7 mols of formaldehyde, said product being obtained by the process of claim 1.

8. A non-resinous condensation product of 1 mol of diphenylamine, 1 mol of N-dimethylaniline and 1 mol of formaldehyde, said product being obtained by the process of claim 4.

9. A non-resinous condensation product of 1 mol of diphenylamine, '1 mols of N-dimethylaniline and 7 mols of formaldehyde, said process being obtained by the process of claim 5.

10. A non-resinous condensation product of 2 mols of diphenylamine, 5 mols 0f N-dimethylaniline and '7 mols of formaldehyde, said product being obtained by the process of claim 6.

11. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sufi'icient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of from 1 to 4 mols of diphenylamine, from 1 to 7 mols of N-dimethylaniline and from 1 to '7 mols of formaldehyde, said product being obtained by the process of claim 1.

12. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a non-resinous condensation product of from 1 to 4 mols of diphenylamine, 1 to 7 mols of N-dimethylaniline, and 1 to '7 mols of formaldehyde, said product being obtained by the process of claim 1.

13. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suflicient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of diphenylamine, 1 mol of N-dimethylaniline, and 1 mol of formaldehyde, said product being obtained by the process of claim 4.

14. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sumcient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of diphenylamine, 7 mols of N-dimethylaniline and '7 mols of formaldehyde, said product being obtained by the process of claim 5.

15. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suflicient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 2 mols of diphenylamine, 5 mols of N-dimethylaniline and 7 mols of formaldehyde, said product being obtained by the process of claim 6.

HERSCHEL G. SMITH. TROY L. CANIREIL. JOHN G. PETERS.

REFERENCES CITED The following references are of record in the file oi this patent:

UNITED STATES PATENTS Number Name Date 1,584,473 Regal May 11, 1928 1,954,484 Mattison Apr. 10, 1984 FOREIGN PATENTS Number Country Date 12,021 Australia Feb. 29, 1928 256,394 Great Britain Aug. 12, 1928 264,958 Italy Mar. 18, 1929 

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTS WHICH COMPRISES HEATING FROM 1 TO 4 MOLS OF DIPHENYLAMINE, 1 TO 7 MOLS OF N-DIMETHYLANILINE, AND 1 TO 7 MOLS OF FORMALDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F TO CONDENSE TOGETHER THE THREE REACTANTS AND RECOVERING THE CONDENSATION PRODUCT. 